The present invention relates to biologically implantable percutaneous connectors, and in particular, such connectors for use with cables including many small electrical conductors.
Recent research has made it desirable to carry electrical signals to or from nervous tissue using many individual electrical conductors, each of which may lead within a person's or animal's body to one or more electrodes associated with living cells, so that artificially produced electrical neural stimulation signals may be carried to such nervous tissue. It is desired, at least for experimental purposes, to use such artificial stimulation of nervous tissue to restore lost hearing or sight. In other instances, it may be possible to use such electrical stimulation to control voluntary muscles.
Electrical conductors may also be used to control or provide power to devices such as pumps used to deliver drugs to specific internal organs.
It is important, however, in establishing electrical connections into the interior of a living person or animal, to minimize the risk of infection by microbes entering the body at the site of a percutaneous conduit. It is therefore desirable to use as few percutaneous conduits as possible, and to connect as many as possible of a required number of electrical conductors through each percutaneous conduit.
At times, particularly in conducting experimental development of electronic devices for stimulating nervous tissue, it will be necessary to disconnect external electrical devices from implanted cables, although it is desirable to leave the implanted cables and electrodes in place in order to avoid the trauma of their removal and replacement.
Pin-and-socket connectors used in the past for applications similar to those described above are undesirably large and difficult to use where more than a very few conductors are concerned, since they require a considerable amount of space and present a likelihood of excessive trauma to an animal or person fitted with such a connector. Such pin-and-socket connectors also present the likelihood of accumulation of harmful microbes on the surfaces of their pins and within the socket cavities.
Other problems with pin and socket connectors are that accidental disconnection of such connectors presents the risk of damage to the pins or sockets, and the forces needed ordinarily for connecting and disconnecting such connectors may tend to disturb implanted connector parts, or else limit undesirably the number of conductors which can be connected through such a connector without such risk.
Accordingly, it is desired to provide a percutaneous connector by which external cables can be disconnected from and reconnected easily to implanted electrical cables, particularly ones which include a large number of small electrical conductors.
The success of a prosthetic device for controlling motor movements or for providing artificial vision or hearing in humans will be in part contingent upon the device's size. Practicality of any device of this type necessitates that components be miniaturized such that the wearer can be mobile and unencumbered by large devices or electrical leads.
The wearer of the device must undergo surgery to have internal electrical leads attached to the appropriate nervous tissue. It is highly advantageous to be able to implant as many internal leads as necessary in one surgical operation thereby obviating the need to perform surgery again. In turn, these electrical leads will be affixed to the percutaneous connector base usually attached to the wearer's skull.
An implantable percutaneous connector, to be practical, must be durable. An implantable percutaneous connector will be subjected to many physical manipulations during the course of its use. During testing of neuroprosthetic devices the percutaneous connectors are subjected to multiple cycles of mating and unmating. Implantable percutaneous connectors made of ceramic material, calcium hydroxy-apatite, or vitreous carbon run the risk of being easily broken or chipped during implantation or by accidental post implantation contact. Titanium, on the other hand, is very durable but will have an impact on the overall size of the connector.
Corbett, III, et al. U.S. Pat. No. 5,274,917 discloses a small connector for multi-conductor cables, but the connector disclosed is not adapted for implantation in living tissue.
In the use of percutaneous connectors it is very desirable to restore and maintain the integrity of the skin surrounding the connectors as a barrier to entry of microbes into the body of an animal or person. It is therefore desirable that tissue surrounding a percutaneous connector should readily attach itself to the surface of an implanted percutaneous connector. While the desirability of such biointegration is well known, it has been difficult to accomplish in the past. Various surfaces have been used in the past in attempts to promote biointegration with greater or lesser degrees of success. For example, Aoki U.S. Pat. Nos. 5,035,711 and 5,026,397 disclose a percutaneous connector having a body formed of sintered hydroxyapatite ceramic material in order to promote biointegration.
Byers U.S. Pat. No. 4,645,504 also discloses a percutaneous conduit fashioned of calcium hydroxyapatite presenting a porous surface intended to promote biological integration as a seal against intrusion of pathogens percutaneously.
Owens U.S. Pat. No. 4,025,964 discloses a percutaneous connector in which a radially extending base flange has holes through which tissue can grow beneath the skin to hold the connector in place, while the separable parts of the connector are held together by magnetic attraction to provide electrical connection through metal contacts.
Parsons U.S. Pat. No. 3,995,644 discloses a percutaneous connector having a body of vitreous carbon in which a neck portion of a reduced diameter is utilized to promote healing of skin around the surface of the connector where it projects through the skin. Within the body of the percutaneous connector a dielectric epoxy adhesive is used to seal the penetration of electrical conductors through the connector body into the tissue of a living organism.
What is desired still, however, is a small percutaneous connector providing the capacity for a relatively large number of electrical conductors, which is easily disconnected and reconnected, and yet which also minimizes the risk of accumulation of contaminants on connector surfaces regardless of whether or not the connector is connected.